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    C1 edexcel

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    yes.

    EDIT: no.
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    (Original post by Pheylan)
    (-27)^{4/3}\not=81
    ahh good point, didn't realise the +- signs woooops
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    (Original post by didgeridoo12uk)
    ahh good point, didn't realise the +- signs woooops
    Okay which part is wrong and whats wrong with it?
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    guys can u please reply, been waiting long.

    thanks
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    (Original post by didgeridoo12uk)
    ahh good point, didn't realise the +- signs woooops
    (Original post by Pheylan)
    (-27)^{4/3}\not=81
    Since when?
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    (Original post by jayseanfan)
    C1 edexcel

    Whenever you see \sqrt{a} or a^{1/2}, it always refers to the positive root. In each case, there should only be one answer, not two.

    The reason you have to use \pm normally is when looking at roots of an equation x^2=c, which arises because of the difference of two squares: if x^2=c then x^2-c=0, so (x-\sqrt{c})(x+\sqrt{c})=0, and hence x = \pm \sqrt{c}. However, throughout this process, \sqrt{c} always refers to the positive root.

    So for example, \sqrt{121}=11, and never -11.
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    (Original post by jayseanfan)
    C1 edexcel

    My values for them were the same as yours, but it wasn't plus/minus, just positive.
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    (Original post by nuodai)
    Whenever you see \sqrt{a} or a^{1/2}, it always refers to the positive root. In each case, there should only be one answer, not two.

    The reason you have to use \pm normally is when looking at roots of an equation x^2=c, which arises because of the difference of two squares: if x^2=c then x^2-c=0, so (x-\sqrt{c})(x+\sqrt{c})=0, and hence x = \pm \sqrt{c}. However, throughout this process, \sqrt{c} always refers to the positive root.

    So for example, \sqrt{121}=11, and never -11.
    This is from the book



    Im very confused?
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    (Original post by jayseanfan)
    This is from the book



    Im very confused?
    Wow... well the book's wrong. At least, the notation a^{\frac{1}{m}} refers to taking the "principal root" which in the case of square roots (and all others) is the positive root.
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    (Original post by Pheylan)
    (-27)^{4/3}\not=81
    -27^\frac13=-3. -3^4= 81
 
 
 
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